1. Field of the Invention
The present invention relates to an information processing apparatus, a processing method for the same, a non-transitory computer-readable storage medium and an image capturing apparatus.
2. Description of the Related Art
Techniques for detecting the line of sight of a person are known. In the technique disclosed in Japanese Patent Laid-Open No. 2008-210239 (referred to below as Document 1), the contour of a face and a plurality of locations, such as the eyes and the like, are detected from edges or the like, and the orientation of the face is detected based on their positional relation. Furthermore, the line of sight of a driver can be detected by detecting the positions of the pupils, taking a camera that is installed in a vehicle as a reference. Moreover, in the technique disclose in Japanese Patent Laid-Open No. 09-081732 (referred to below as Document 2), an eye region is detected using an energy model, and a line of sight is detected by comparing this eye region with a predetermined image dictionary.
Japanese Patent Laid-Open No. 2006-293909 (referred to below as Document 3) describes a technique for detecting a line of sight that takes into account the influence individual differences known as the dominant eye. In the technique disclosed in Document 3, the line of sight of a driver is detected based on pre-registered information that indicates whether the left or the right eye is the dominant eye, on the premise that the orientation of the driver's face is facing straight ahead. Furthermore, Japanese Patent Laid-Open No. 2001-051338 (referred to below as Document 4) describes a technique relating to an image capturing apparatus that utilizes such a technique for detecting lines of sight. With the technique disclosed in Document 4, image capturing is carried out when the line of sight of an object faces in the camera direction.
As shown in FIG. 13A, the direction (orientation) of the line of sight of an object taking a predetermined direction as a reference can be represented as a line-of-sight direction (θ1, θ2). Moreover, as shown in FIG. 13B, the line-of-sight orientation (θ1, θ2) of the object can also be represented by the orientation (α1, α2) of the face and the orientation (β1, β2) of the eyes. There is a possibility that shifts due to individual differences occur in the orientation (α1, α2) of the face and the orientation (β1, β2) of the eyes, which are necessary in order to detect the line-of-sight orientation (θ1, θ2) of the object.
Here, several examples of such individual differences are given. An example of a first individual difference is differences in the size of facial organs, such as the facial bones, eyes (pupils) or mouth, as well as differences in the positional relationship of these facial organs, as shown in FIG. 14A. The orientation (α1, α2) of the face and the orientation (β1, β2) of the eyes are often detected utilizing averaged positional relationships of such facial organs as the eyes (pupils) or the mouth, or averaged dictionary data serving as a model. Therefore, when face whose line of sight is to be detected deviates from the averaged positional relationship of the facial organs or the averaged dictionary data, then there is a possibility that a shift occurs in the orientation (α1, α2) of the face or the orientation (β1, β2) of the eyes.
An example of a second individual difference is the dominant eye. It is said that people use the field of vision obtained with one eye as the main visual information. The eye with that obtains this main visual information is called the “dominant eye.” Therefore, it is said that if a person looks at a predetermined object, the dominant eye looks in the direction of that predetermined object, but the other eye looks in a direction that is shifted slightly away from the direction of the predetermined object. For example, even though the two people shown in FIG. 14B look straight ahead, in the person on the left in FIG. 14B, the right pupil is located at the center of the eye region, but the left pupil is located to the left from the center of the eye region. Similarly, in the person on the right in FIG. 14B, the left pupil is located at the center of the eye region, but the right pupil is located to the right from the center of the eye region. Furthermore, there are also people with no constant dominant eye, whose dominant eye alternates between left and right. Due to individual differences in the dominant eye, shifts occur in the orientation (β1, β2) of the eyes.
If such a line-of-sight detection technique is applied to various types of apparatuses, then several problems may occur due to these individual differences. For example, if applied to an image capturing apparatus that automatically performs image capturing when the line-of-sight orientation faces in the camera direction, there is a possibility that the problem occurs that no image is captured even though the object looks in the camera direction. Moreover, if applied to an in-vehicle apparatus for sounding an alarm upon the detection of look-away, there is the possibility that look-away is erroneously detected and the alarm may be sounded continuously, even though the object looks straight ahead.